In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, brown sugar, and granulated sugar together on high speed until well mixed, about 2 minutes.
¾ cup unsalted butter, ¾ cup brown sugar, ¼ cup granulated sugar
Beat in the pumpkin, egg, and vanilla extract until creamy, about 2 minutes. Set aside.
½ cup pure pumpkin puree, 1 large egg, 1 teaspoon pure vanilla extract
In a large bowl, stir together the flour, dry pudding mix, pumpkin pie spice, baking soda, cornstarch, and salt.
2⅓ cups all-purpose flour, 3.4 ounces dry vanilla instant pudding mix, 2 teaspoons pumpkin pie spice, 1 teaspoon baking soda, 1 teaspoon cornstarch, ½ teaspoon kosher salt
Pour the dry ingredients into the wet ingredients and stir just until combined. Try to avoid overmixing so the cookies stay soft and chewy.
Stir in 1 cup of the white chocolate chips. Set the other ¼ cup of white chocolate chips aside to top the cookies before baking.
1¼ cups white chocolate chips
Line a baking sheet that can fit into your freezer with parchment paper. Use a 2-tablespoon-sized cookie scoop to scoop evenly-sized cookies onto the prepared baking sheet. Place all of the cookies onto a single baking sheet (not touching each other).
Use the remaining ¼ cup of white chocolate chips to press extra chocolate chips into the top of each cookie. The cookie dough should be in balls - do not flatten the cookie dough balls at all.
Place the tray of cookie dough in the freezer for 10 minutes. This will help the cookies keep their shape while baking.
While the cookies chill, preheat oven to 350°F.
Line a second baking sheet with parchment paper and place some of the cookie dough balls from the freezer onto the baking sheet. The cookies should be 3 inches apart from each other.
Bake one sheet of cookies at a time for 12-14 minutes, or until the edges are set. The bottoms will be slightly brown but the tops of cookies will still look slightly wet. They’ll continue to bake on the hot tray after removing the cookies from the oven.
Let cookies cool completely on baking sheets before transferring to a food safe container for storage.